Fibre Characterisation of Pulp Logs Using Acoustics

A scoping trial sorted peeler cores according to speed of sound. Subsequent pulping and testing showed that fibre length, pulp strength and various properties of handsheets varied systematically with the velocity of sound along the logs. For example, the average fibre length ranged from 1.8 to 2.6 mm at the two extremes of sound groups. Where the sound travelled slowly along the log the fibre length was short and vice versa. Here we report laboratory and mill trials. First the pulp characteristics of slabwood chip from acoustically sorted logs are determined, and then the results of two mill trials using large numbers of pulp logs are discussed. The two mill trials while substantiating the earlier work did not produce such decisive improvements in fibre sorting as observed with the peeler cores. Overall, acoustics offers the prospect of better fibre allocation according to end-use, and the prospect that, with more closely characterised pulps, papers will have more uniform properties. Acoustic tools provide a totally new and effective means of allocating individual logs to the process for which the fibre is best suited.